

package com.hazelcast.jet.impl.util;

import com.hazelcast.jet.core.Inbox;

import javax.annotation.Nonnull;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Iterator;

/**
 * An {@link Inbox} implementation backed by an {@link ArrayDeque}.
 */
public final class ArrayDequeInbox implements Inbox {

    private final ProgressTracker progTracker;
    private final ArrayDeque<Object> queue = new ArrayDeque<>();

    /**
     * Constructs the inbox with the provided progress tracker.
     */
    public ArrayDequeInbox(ProgressTracker progTracker) {
        this.progTracker = progTracker;
    }

    @Override
    public boolean isEmpty() {
        return queue.isEmpty();
    }

    @Nonnull
    @Override
    public Iterator<Object> iterator() {
        return queue.iterator();
    }

    @Override
    public Object peek() {
        return queue.peek();
    }

    @Override
    public Object poll() {
        Object result = queue.poll();
        progTracker.madeProgress(result != null);
        return result;
    }

    @Override
    public void remove() {
        queue.remove();
        progTracker.madeProgress();
    }

    @Override
    public void clear() {
        queue.clear();
        progTracker.madeProgress();
    }

    /**
     * Retrieves the queue backing this inbox.
     */
    public Deque<Object> queue() {
        return queue;
    }

    @Override
    public int size() {
        return queue.size();
    }
}
